1. Field of the Invention
The present invention relates generally to irrigation devices, and more particularly to the communication of data using an alternating power signal to be supplied to irrigation devices.
2. Discussion of the Related Art
Typical irrigation control systems cooperate with water valves and pumps to control the flow of irrigation water through a variety of water dispensing devices, including sprinklers, rotors, drip-lines, and other water delivery devices. These control systems are used in a wide variety of irrigation applications, from residential and commercial landscapes to golf course and agricultural irrigation.
Many irrigation systems and electronics are powered by 50/60 Hz AC voltage signals. Some systems further modulate this power source to provide data communication, for example, by selectively clipping the positive half of the AC voltage signal. Data and power sent in this manner are often over a two-wire transmission line and are often referred to as a two-wire interface. Irrigation devices variously located in the field couple to the two-wire interface and derive their operational power therefrom. The irrigation devices demodulate the data monitoring the received power signal for a missing negative half of a cycle, then taking eight voltage samples at a predetermined time thereafter during the positive half to detect whether the signal is clipped or unclipped. Such systems are well known in the art and described for example in U.S. Pat. No. 4,176,395 to Evelyn-Veere.